It is well known to wear a medallion attached to a necklace, and it is also known for the medallion to electronically show an image. Typically, a backlight in the medallion is turned on by pressing a button, and then the device stays on for a certain limited period of time.
Such a medallion must typically be small in size, in order to comfortably and fashionably attach to a necklace. However, this small size limits battery capacity, which in turn limits the time during which the display can remain backlit. A typical battery will allow the medallion to be fully backlit for only ninety (90) minutes, or for three (3) hours with half brightness.
When the backlight is off, the image may still be somewhat visible when there is sufficient ambient light in the environment, because a display can operate reflectively without backlighting. However, the visibility is poor for color images in reflective mode, and it is then difficult for a person to recognize the reflective image in an indoor lighting environment. Likewise, no matter how good the display is in reflective mode, there will always be environments—such as a bar—where there is not enough ambient light to see the image reflected from the medallion's display. Therefore, the limited reflective properties of a transflective Liquid Crystal (LCD) display do not eliminate the need to extend the operating life beyond three hours.
It is known to slightly vary the brightness of an LCD display in order to decrease prolonged eye strain. The idea is that when the LCD image has a different brightness, then different eye muscles will be used for viewing, and thus varying the brightness slightly will allow previously used eye muscles to rest. See Wagner (U.S. Pat. No. 5,933,130). However, for a person wearing or observing a medallion, there is no problem of prolonged eye strain. Moreover, the slight variations of brightness in Wagner will not have a significant impact on energy consumption or battery life.
It is known to reduce the power input into an image display in order to prolong battery life. See Godfrey (U.S. Pat. No. 5,736,973). However, such known transflective LCD technology requires that the power input be changed based upon the amount of enivronmental lighting, rather than based upon other factors, and moreover requires that the environmental lighting be monitored by a sensor or by the user.